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Table 11.1 Local anesthetic agents
Local anesthetic agents
Onset
Agent
Amides
Lidocaine 5–10min 1–3 h 5 mg/kg and
Bupivicaine 5–10min 3–10 h 2–3 mg/kg Inltration,
Prilocaine 2–4min 1–2 h 8 mg/kg;
Esters
Cocaine 5–10min 30–
Benzocaine 5–10min 30–
Tetracaine 5–10min 30min 20mg single
time Duration
60min
60min
Maximum
dose Uses Notes
Inltration,
7 mg/kg
with
epinephrine
600mg
maximum
adult dose
2–3 mg/kg Topical anesthetic
200mg Topical airway
dose
peripheral nerve
blockage,
epidural
anesthesia,
topical (ointment
or viscous),
nebulized for
airway anesthesia
peripheral nerve
blockage,
epidural
anesthesia
Similar to
lidocaine
EMLA cream:
mixture of
lidocaine 2.5%
and prilocaine
2.5% emulsion
used to decrease
pain associated
with venipuncture
to mucosal
surfaces
anesthetic or
ointment for
dressings
Aerosol for
topical anesthesia
of upper airway;
also as
ophthalmic
anesthesia
189
Can cause
methemoglobinemia
At low concentrations,
provide sensory block
only, at higher
concentrations, provide
sensory and motor block.
Cardiotoxic at high doses
Can cause
methemoglobinemia at
dose equal or greater than
600mg
Causes vasoconstriction.
Blocks reuptake of
norepinephrine and
dobutamine at adrenergic
nerve (tachycardia,
hypertension)
Can cause
methemoglobinemia
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Supraorbital andSupratrochlear Nerve Block
• Typically used for forehead anesthesia
• Palpate supraorbital notch, and then insert needle until paresthesias are felt in
distribution → injection of 3ml of 2% lidocaine with epinephrine
Infraorbital Nerve Block
• Used commonly in rhinoplasty and sinus procedures
• Targets the V2 distribution innervating the skin and soft tissue of midface
• Infraorbital nerve exits foramen just below infraorbital rim at pupillary line
Sphenopalatine Nerve Block
• Ganglion located within the pterygopalatine fossa.
• Palpate for depression in the hard palate just medial to gumline at 2nd molar; this
indicates greater palatine foramen. Bend needle at 2.5cm at 45° to avoid damage
to orbital structures superiorly.
Otologic Nerve Blocks
A. Wong et al.
• Sensory innervation derived from greater auricular and auriculotemporal nerve
(external) and branches of 7th, 9th, and 10th cranial nerves (EAC)
• Injection performed around the ear circumferentially for external block
Laryngeal Nerve Blocks
• Largely supplied by the superior laryngeal nerve with small contribution of the
recurrent laryngeal nerve.
• Typically a combined transtracheal and superior laryngeal nerve block is used.
• Cricothyroid membrane is palpated, and 2–4 cc of 4% lidocaine is injected—a
“popping” sound can be appreciated upon entrance of the needle into the trachea.
• Midway between the hyoid and thyroid cartilage, an additional 2 cc of local is
injected.
General Anesthesia
• Four main stages of anesthesia:
– Stage 1: Conscious and rational, perception of pain diminished
– Stage 2: Unconscious but responds to stimuli, (+) breath holding, (+) pharyngeal
muscular tone, able to protect airway, pupils dilated and gaze discongugate
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– Stage 3: Surgical anesthesia—increasing degrees of muscular relaxation, (−)
protective pharyngeal reexes, unable to protect airway
– Stage 4: Medullary depression—cardiovascular and respiratory collapse
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Inhalation Anesthetic Agents
• See Table11.2 Inhalation anesthetic agents.
• Potency: described by MAC (minimal alveolar concentration)—concentration of
anesthetic that will prevent movement in response to surgical stimuli in 50 % of
individuals.
• Solubility: described by blood/gas partition coefcient—ratio of anesthetic concentration in blood to alveolar space when their partial pressures are in
equilibrium.
– The higher the partition coefcient, the higher the solubility.
– Lower the solubility → reach equilibrium faster →faster onset/offset.
• Agents are additive—2 drugs with 1/2 MAC of each will deliver 1 MAC.
• 0.3–0.5 MAC usually enough to prevent awakening or awareness.
Intravenous Anesthetic Agents
• See Table11.3 Intravenous anesthetic agents.
• Typically used in conjunction for induction.
• Provides hyponosis and blunting of reexes.
Neuromuscular Blocking Agents
• Allows interruption of transmission of synaptic signaling at neuromuscular
junction
Depolarizing Neuromuscular Blocking Agents
• Succinylcholine
– Mechanism of action (MOA): Binds to postsynaptic nicotinic acetylcholine
receptors at neuromuscular junction, prevents depolarization of motor
end plate.
– Pharmacokinetics: Very rapid onset (30–60 s), very short duration (4–6 min).
Degradation by plasma pseudocholinesterases.
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Table 11.2 Inhalational anesthetic agents
Inhalation anesthetic agents
Blood: gas
partition
Agent MAC%
Nitrous oxide
(non-volatile
gas)
Desurane 6.0 0.42 Similar to isourane. But
Sevourane 2.0 0.65 Mild respiratory and
Isourane 1.2 1.4 Suppresses respiratory
Halothane 0.75 2.30 Moderate cardiac
105 0.47 Mild myocardial
coefcient Systemic effects Notes
depression, minimal
effect on respiration
at high concentrations,
tachycardia and
hypertension due to
sympathomimetic
properties
cardiac depression,
potent bronchodilator
drive and ventilator
response to hypoxemia,
direct cardiac depressant,
reduces systemic
vascular resistance,
potent vasodilator
depression. Risk of
severe bradycardia at
high concentrations.
A. Wong et al.
• Often used in combination
with other inhaled,
intravenous agents or
narcotics
• Not pungent
• Higher incidence of
postoperative nausea/
vomiting
• Analgesic and anxiolytic
properties. No amnestic
effects
• Fastest onset/offset
• Most pungent →
bronchoirrative with high
incidence breath-holding,
coughing, laryngeal spasm
• Good for maintenance of
anesthesia for short cases
due to ease of titration
• Least pungent
• Best for induction,
especially in pediatric
patient
• Most commonly used
volatile inhaled agent in
developed countries
• Slower onset/offset and
high fat solubility →
decrease near end of case
to prevent prolonged
awakening
• Good for maintenance of
anesthesia for long cases
due to very low cost, most
potent of volatile
anesthetics
• Slow onset/offset
• No longer used in North
America due to adverse
effects (hepatotoxicity,
halothane hepatitis).
Mainly used in resourcepoor countries
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Table 11.3
Intravenous anesthetic agents
Agent
Propofol Facilitate
Etomidate Enhances
Ketamine Noncompetitive
Thiopenthal Enhances
Intravenous anesthetic agents
Mechanism of
action Pharmacokinetics
inhibitory
neurotransmission
by enhancing
GABA receptors
in CNS.Also
anatogonist of
NMDA receptor
inhibitory
neurotransmission
by enhancing
GABA receptors
in CNS
antagonist of
NMDA receptors
in CNS
inhibitory
neurotransmission
by enhancing
GABA receptors
in
CNS.Ultrashortacting barbiturate
Rapid onset, short
duration, rapid
recovery
Rapid onset, short
duration, rapid
recovery
Rapid onset, short
duration, rapid
recovery
Rapid onset, short
duration, rapid
recovery (except
with prolonged
infusion)
Systemic
effects Notes
Decrease BP
via
vasodilation,
minimal effect
on HR,
dose-dependent
respiratory
depression,
anticonvulsant,
bronchodilator
Does not
change BP, HR,
or CO,
anticonvulsant
Increase
sympathetic
tone → increase
HR, BP, CO,
bronchodilator,
no respiratory
depressant
effect
Decrease BP
via
vasodilation,
minimal effect
on HR,
anticonvulsant,
respiratory
depression
Lower incidence
of postoperative
nausea/vomiting
High incidence of
postoperative
nausea/vomiting,
no analgesic
effect, can
produce
myoclonic
movements on
induction, causes
transient
adrenocortical
suppression
Associated with
unpleasant
dreams/
hallucinations
after emergence
(add
benzodiazepine to
reduce incidence),
has analgesic
effect, can
increase
intracranial
pressure
No longer
available in the
USA, generally
reserved for
electroconvulsive
therapy, lowers
seizure threshold
(continued)
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Table 11.3 (continued)
Intravenous anesthetic agents
Agent
Dexmedetomidine Alpha-2
GABA Gamma-aminobutyric acid, NMDA N-methyl-D-aspartate, BP blood pressure, CO cardiac
output, HR heart rate
Mechanism of
action Pharmacokinetics
adrenergic agonist,
inhibits release of
norepinephrine
Systemic
effects Notes
Decreases BP
and HR, very
mild respiratory
depressant
effect
A. Wong et al.
New sedative
hypnotic
approved for
short-term ICU
use, helps wean
off mechanical
ventilator and
other sedatives
faster, needs
continuous
infusion
– Side effects: Bradyarrythmias, myalgias, hyperkalemia, malignant hyperther-
mia. Be cautious of use in patients with spinal cord injuries, major burns, and
genetic neuromuscular disorders (risk of fatal hyperkalemia) and those with
decreased pseudocholinesterase activity, liver failure, and malnutrition (risk
of prolonged paralysis).
– Notes: Paralysis preceded by muscle fasciculation, used for rapid sequence
induction. In smaller doses, can be used to relieve laryngospasm.
Non-depolarizing Neuromuscular Blocking Agents
• MOA: Reversible competitive antagonism of acetylcholine.Protects endplate
from depolarization by acetylcholine ➔ accid paralysis.
• Atracurium:
– Pharmacokinetics:
Onset: 60–120 s
Duration: >30min
Uninuenced by the liver or kidneys
– Notes: Minimal cardiovascular effects. Higher doses → histamine release →
hypotension, bronchospasm
• Rocuronium:
– Pharmacokinetics:
Onset: 60–90 s
Duration: 45–75min
Biliary and renal elimination
– Notes: Minimal cardiovascular effects
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• Vecuronium:
– Pharmacokinetics:
Onset: 90–180 s
Duration: 30–40min
– Notes: No cardiovascular effects, no histamine release
• Cistracurium:
– Pharmacokinetics:
Onset: 90–120 s
Duration: 60–80min
– Notes: Stereoisomer of atracurium. Less prone to cause histamine release
• Mivacurium:
– Pharmacokinetics:
Duration: 10–15min
Metabolized by plasma cholinesterase
– Notes: Mild hypotension due to histamine release. Unavailable in the USA
• Non-depolarizing neuromuscular blocking agents may be reversed with the use
of cholinesterase inhibitors, which increase available acetylcholine at neuromus-
cular junction.
– Examples: Edrophonium, neostigmine, pyridostigmine.
– Anticholinergic drugs (glycopyrrolate or atropine) should accompany use of
cholinesterase inhibitors to alleviate its parasympathetic muscarinic side
effects.
• Monitor peripherally by electronically stimulating the ulnar nerve and measuring
adductor pollicis response.
– Monitor the decreased twitch height or fade of “train-of-four” twitches.
– Twitch response correlates with percentage of neuromuscular blockade.
• Complications:
– Malignant hyperthermia
Hypermetabolic syndrome secondary to increases in Ca2+ in sarcoplasmic
reticulum.
Autosomal dominant, variable expressivity.
Offending agents include halogenated inhaled agents and succinylcholine.
Features include tachycardia, hypercarbia, metabolic acidosis, muscle
rigidity, hypoxemia, hyperkalemia, and ventricular dysrhythmias.
Treatment: dantrolene, sodium bicarbonate administration, insulin, and
glucose.
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A. Wong et al.
Muscular dystrophy patients have increased risk.
– Laryngospasm
Typically due to irritative stimulus to airway during light anesthesia
Triggers: secretions, vomitus, blood, pungent volatile anesthetics,
laryngoscopy
Treatment: Remove stimulus, administer 100% oxygen, continuous positive pressure on airway and jaw thrust
Opioids
• See Table11.4 Opioids.
• Provides analgesia, produce unconsciousness, and suppress response.
• Used as a supplement during induction or maintenance.
• Binds to mu-receptors in the brain, spinal cord, and periphery.
• Onset within minutes and metabolism via the liver and eliminated by the kidneys.
• Minimal affect to cardiovascular but dose-dependent depression of respiration.
Table 11.4 Commonly used opioids
Opioids
Potency
relative to
Agent
Morphine 1
Codeine 0.1 Biotransform to morphine in
Hydromorphone 5 Intravenous:
Oxycodone 1.5
Fentanyl 100 Onset time: 30 s
Remifentanil 100 Rapidly hydrolyzed by
Meperidine 1/10 Eliminated by liver and
MAOI monoamine oxidase inhibitors
morphine Pharmacokinetics Notes
Has strong cough-suppressant
liver (10%)
Peak effect: 20–30min
Duration: 2–3 h
Peak effect: 3–5min
Eliminated by liver
plasma and tissue esterases
→ rapid onset and recovery.
Metabolism unaffected by
renal or hepatic function
kidney
properties
Codeine derivative. Can be useful
alternative in patients needing
higher opioid doses
Also comes in transdermal
delivery system
Antitussive properties. Consider
adding longer-acting opioid prior
to awakening to provide
postoperative pain control
Direct myocardial depression,
tachycardia. + Histamine release.
Rarely used for pain now due to
risk of serotonin syndrome
(especially when combined with
MAOIs). Only used at low doses
to treat postoperative shivering
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Pharmacology
Antibacterials
• See Table11.5 Antibacterial drugs.
• Bacteriostatic:
– MOA: Prevents replication of bacteria
– Functions best during growth phase
• Bacteriocidal:
– MOA : Actively kills pathogen
– Treats both multiplying and non-multiplying bacteria
Antifungals
• See Table11.6 Antifungal drugs.
Antivirals
197
• See Table11.7 Antiviral drugs.
Medication forTreatment ofGastric Acidity
• See Table11.8 Commonly used anti-reux medications.
Commonly Used Rhinologic Medications
Antihistamines
• MOA: dose-dependent antagonism of histamine-1 receptor (Table11.9)
• First-generation oral antihistamines
– Examples: diphenhydramine, chlorphenriamine
– Side effects: anticholinergic (constipation, dry mucous membrane, blurry
vision), sedation (crosses the blood-brain barrier easily), tachyphylaxis
(decreaed efcacy with continued use)
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Hypersensitivity (~5%), ampicillin
associated rash with concurrent
mononucleosis infection
Time-dependent killing, CNS
penetration, gram (+), gram (−),
spirochetes, resistance with microbial
beta-lactamase enzyme production
GI (nausea, vomiting, diarrhea)—
minimized with concurrent meal
Gram (+) and gram (−) aerobes/
anaerobes, +/− Pseudomonas
Gram (+), skin ora Nausea
Diarrhea
Less gram (+) and more gram (−), not
Risk of Pseudomembranous colitis
Pseudomonas or penicillin-resistant
Streptococcus pneumonia
Gram (−), (+) CSF penetration, no
pseudomonas coverage
A. Wong et al.
Non-ototoxic alternatives to
gentamicin for pseudomonas coverage
Seizures (high doses)
Broad spectrum, typically for severe
infections, not rst line
Beta-lactam inhibits -alanyl--
alanine carboxypeptidase which
cross links peptidoglycan
Amoxicillin
Dicloxicillin
Methicillin
Oxacillin
Penicillin
Antibacterials
Class Names MOA Efcacy Side Effects
Table 11.5 Antibacterial drugs
Penicillins Ampicillin
Irreversibly bind to beta-
lactamase enzymes inhibiting
activity
Amoxicillin/
clavulanate
Ampicillin/
sulbactam
Piperacillin/
tazobactam
Ticarcillin/
clavulanate
Penicillin +
Beta-Lactamase
inhibitor
Cephalosporins Beta-lactam cell wall synthesis
inhibitor
First generation Cefazolin
Cephalexin
Second generation Cefoxitin
Cefprozil
Cefuroxime
Third generation Cefdinir
Cexime
Ceftazidime
Ceftriaxone
Beta-lactam cell wall synthesis
inhibitor
Imipenem
Meropenem
Fourth generation Cefepime Antipseudomonal
Carbapenems Ertapenem
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